This application is based upon, claims the benefit of priority of, and incorporates by reference, the contents of Japanese Patent Applications No. 2002-117588 filed Apr. 19, 2002.
1. Field of the Invention
The present invention relates to a vehicle air-conditioning system of a cold storage type which comprises a cold storage area to be cooled by cold air that passes through a cooling evaporator, and is suitably applied to a vehicle which temporarily stops its vehicle engine, as a compressor driving source, during vehicle stops.
2. Description of the Related Art
For the purposes of protecting the environment and saving fuel, vehicles that stop their engines automatically during vehicle stops, such as at stoplights for example, are called eco-run vehicles. Therefore, xe2x80x9cEco-runxe2x80x9d stands for xe2x80x9cECOlogical-runxe2x80x9d and xe2x80x9cECOnomy-run.xe2x80x9d Eco-run vehicles include hybrid vehicles whose practical, overall use has been increasing.
Normally, the compressor on the refrigeration cycle of a vehicle air-conditioning system is driven by the vehicle engine. With the foregoing eco-run vehicles, each time the vehicle engine is stopped during a vehicle stop, at say, a stoplight, the compressor is also stopped. It follows that the cooling evaporator rises in temperature, and the temperature of the air blown into the passenger compartment increases. This causes a problem in that the cooling of the passengers stops.
There has been a growing need for a vehicle air-conditioning system of a cold storage type which has cold storage for storing coolness (cold heat) when the compressor is in operation, and that can cool the air blown into the passenger compartment by discharging the cold heat stored in the cold storage when the compressor is stopped, that is, when the cooling operation of the cooling evaporator is stopped.
The inventors are currently working on the development of a cold storage type vehicle air-conditioning system mentioned above. When the cold heat stored in the cold storage runs out and the cooling operation stops when the vehicle stops, the outlet air temperature of the cold storage increases. Then, an operation request signal of the vehicle engine is issued to restart the vehicle engine when the outlet air temperature of the cold storage rises to the cooling upper target temperature, such as 18xc2x0 C., during vehicle stops. Restarting the engine also restarts the compressor, and the cooling evaporator resumes its cooling operation. The loss of air conditioning during vehicle stops can thus be prevented from occurring.
When a stopped vehicle engine is abruptly restarted, when the vehicle is stopped, by the operation request signal from the air-conditioner, passengers may experience an odd or uncomfortable feeling. It is therefore desired that the time over which the cold storage can cool the interior of the compartment by means of discharge of the cold heat stored therein, i.e., the cold discharge cooling remaining time of the cold storage, be calculated and made known to passengers. In this case, it is desired to establish precise agreement between the instant when the indication of the cold discharge cooling remaining time becomes zero and the instant when the vehicle engine is restarted.
In view of this, the inventors have made the following study in order to calculate the cold discharge cooling remaining time of the cold storage for indication to the passengers. FIG. 7 shows how the outlet air temperature of the cold storage behaves when the vehicle is running and when the vehicle is undergoing an eco-run halt. Here, the eco-run halt refers to the state when the vehicle engine is automatically stopped when the vehicle stops.
In FIG. 7, To is the solidifying point, e.g. 8xc2x0 C., of the cold storage medium contained in the cold storage. When the compressor is driven by the vehicle engine when the vehicle starts running, cold air cooled by the cooling operation of the evaporator passes through the cold storage to cool the cold storage medium. As a result, the outlet air temperature of the cold storage drops toward the solidifying point To of the cold storage medium as seen in the range a.
When the outlet air temperature of the cold storage falls to the solidifying point To, the cold storage medium starts a phase change from a liquid phase to a solid phase (i.e., solidification). The cold heat is thus stored into the cold storage medium in the form of latent heat of solidification. After the start of this solidification, the outlet air temperature of the cold storage is maintained at generally constant temperatures near the solidifying point To of the cold storage medium as seen in the range b. When the cold storage medium completes solidification, it starts to make a sensible heat change. The outlet air temperature of the cold storage drops again toward the outlet air temperature of the evaporator as seen in the range c.
Next, when the vehicle comes to a stop to begin an eco-run halt (i.e., an engine stop), a cold discharge cooling mode is started to cool the interior of the compartment by means of discharge of the cold heat stored in the cold storage. The range d is one in which the cold storage medium makes a sensible heat change. The outlet air temperature of the cold storage thus rises to near the solidifying point To in a short time. Subsequently, the cold storage medium starts a phase change from the solid state to the liquid state (i.e., melting). The cold storage medium thus absorbs latent heat of melting from the air passing through the cold storage.
While the cold storage medium continues melting, the outlet air temperature of the cold storage is maintained at generally constant temperatures near the solidifying point To as shown in the range e. When the cold storage medium completes melting, it starts to make a sensible heat change. The outlet air temperature of the cold storage thus goes up as seen in the range f.
When the outlet air temperature of the cold storage rises to a predetermined cooling upper target temperature TA during the eco-run halt, the operation request signal of the vehicle engine is notified to restart the vehicle engine. Here, the cooling upper target temperature TA is a limit temperature at which passengers start to feel uncomfortable. This temperature, for example 18xc2x0 C., is determined from sensory evaluations by a plurality of subjects.
Hence, the cold discharge cooling remaining time tx of the cold storage is the time between the current point of eco-run halt and the instant when the outlet air temperature of the cold storage reaches the cooling upper target temperature TA mentioned above. In FIG. 7, tx shows the maximum time from the point immediately after the eco-run halt, or rather, the maximum time from the point of eco-run halt until the temperature TA.
It is possible to calculate the cold discharge cooling remaining time tx from changes in the outlet air temperature of the cold storage. Nevertheless, since the outlet air temperature of the cold storage rises at inconsistent rates, the rate of decrease of the remaining time tx is also inconsistent. Thus, the cold discharge cooling remaining time tx cannot be calculated and indicated with accuracy.
To be more specific, the remaining time tx can be calculated by the following equation:
tx=(TAxe2x88x92Tnow)/xcex94tc,
where Tnow is the cold storage outlet air temperature at present, TA is the cooling upper target temperature, and xcex94tc is the amount of change (xc2x0 C./second) of the cold storage outlet air temperature at present per unit time (1 second).
According to this calculation method, however, the cold discharge cooling remaining time tx cannot be calculated and indicated with accuracy. For example, even if tx is determined to be 30 seconds at time t1 in FIG. 8, the calculation is erroneous due to the presence of the subsequent range e where the outlet air temperature of the cold storage is maintained at generally constant temperatures near the solidifying point To by the latent heat of melting of the cold storage medium.
For another method of calculating the cold discharge cooling remaining time tx, the cold heat stored into the cold storage medium while the vehicle is running, or during engine operation, is calculated from factors such as the suction air temperature of the cold storage, the rate of air passing through the cold storage, and the cold storage time. The cold heat discharged from the cold storage medium during an eco-run halt is calculated from factors such as the suction air temperature of the cold storage, the rate of air passing through the cold storage, and the cold discharge time. Remaining cold heat is determined from a difference between the stored cold heat and the discharged cold heat.
Then, the cold discharge cooling remaining time tx can be calculated from the remaining cold heat and the cold heat to be discharged per unit time. Even in this calculation method, however, the stored cold heat and the discharged cold heat are no more than indirect estimations. Deviations can easily occur between the actual amounts of the stored cold heat, the discharged cold heat and the calculations thereof due to various factors including detection errors of the cold storage suction air temperature and response delays in temperature detection.
Consequently, the deviations occurring in the calculations preclude accurate calculation of the cold discharge cooling remaining time tx. Then, precise agreement cannot be established between the instant when the cold discharge cooling remaining time tx=0 and the instant when the actual outlet air temperature of the cold storage rises to the cooling upper target temperature TA to restart the vehicle engine. The result is that the indication of the cold discharge cooling remaining time tx loses its meaning (accuracy).
Japanese Patent Laid-Open Publication No. Hei 2-29578 discloses a method of calculating and displaying the remaining cold insulatable time of a cold storage medium in the field of a cold storage type refrigerator. The concept underlying the method of calculating the remaining cold insulatable time according to this conventional art is, however, basically the same as with the latter calculation method based on the remaining cold heat described above. This conventional technology, even if applied to the method of calculating the cold discharge cooling remaining time tx of the cold storage medium in the cold storage type vehicle air-conditioning system, produces the same problem as with the latter calculation method.
As a result of the preceding problems, the present invention has been developed. It is thus an object of the present invention to provide a cold storage type vehicle air-conditioning system in which the cold discharge cooling remaining time of the cold storage during an eco-run halt is accurately calculated.
Another object of the present invention is to provide a cold storage type vehicle air-conditioning system in which the cold discharge cooling remaining time of the cold storage during an eco-run halt is accurately indicated.
To achieve the foregoing object, a first aspect of the present invention is to provide a vehicle air-conditioning system to be mounted on a vehicle which exercises control to stop its engine (4) at a halt, that is, when the vehicle stops. The air-conditioning system has a compressor (1) to be driven by the vehicle engine (4). A cold storage (40) is disposed downstream of airflow of an evaporator (9) in a refrigeration cycle (R). The cold storage (40) has a cold storage medium (44) to be cooled and solidified by cold air after the sir passes the evaporator (9). The air-conditioning system enters a cold discharge cooling mode to cool the air blown into a passenger compartment by using cold heat stored in the cold storage (40) when the vehicle engine (4) is stopped. Additionally, the air-conditioning system issues an operation request signal to the vehicle engine (4) when the temperature of the cold storage (40) rises to a predetermined upper target cooling temperature in the cold discharge cooling mode.
The air-conditioning system further comprises first calculation means (S100), second calculation means (S110), and remaining time selecting means (S120, S130, S160, S170, S180). The first calculation means (S100) calculates the remaining cold heat in the cold discharge cooling mode from the cold heat stored in the cold storage medium (44) when the vehicle engine (4) is operating, and when cold heat is being discharged from the cold storage medium (44) when the vehicle engine (4) is stopped, and then calculates the remaining time of the cold discharge cooling mode from the remaining cold heat.
The second calculation means (S110) calculates the remaining time of the cold discharge cooling mode from temperature changes of the cold storage (40), and sets the remaining time to zero when the temperature of the cold storage (40) rises to the cooling upper target temperature. The remaining time selecting means (S120, S130, S160, S170, S180) selects the remaining time determined by the first calculation means (S100) in the cold discharge cooling mode as long as the temperature of the cold storage (40) is lower than a temperature near the solidifying point of the cold storage medium (44), and selects the remaining time determined by the second calculation means (S110) when the temperature of the cold storage (40) exceeds the temperature near the solidifying point of the cold storage medium (44).
Consequently, the remaining cold heat in the cold discharge cooling mode is calculated by the first calculation means (S100) until the cold storage medium (44) of the cold storage (40) finishes melting, i.e., a phase change from a solid phase to a liquid phase. The remaining time of the cold discharge cooling mode is calculated based on this remaining cold heat. Thus, even when the temperature of the cold storage (40) is maintained at constant temperatures near the solidifying point To by means of latent heat of solidification of the cold storage medium (44), the cold discharge cooling remaining time, which decreases with a decrease in the remaining cold heat, can be accurately calculated. It is therefore possible to calculate the cold discharge cooling remaining time properly even if the temperature of the cold storage (40) is maintained at generally constant temperatures near the solidifying point To by means of latent heat of solidification of the cold storage medium (44) in the cold discharge cooling mode.
When the temperature of the cold storage (40) exceeds the temperature near the solidifying point of the cold storage medium (44) in the cold discharge cooling mode, the second calculation means (S110) calculates the cold discharge cooling remaining time from temperature changes of the cold storage (40). Besides, the second calculation means (S110) sets the cold discharge cooling remaining time to zero when the temperature of the cold storage (40) rises to the cooling upper target temperature. Precise agreement can thus be established between the instant when the temperature of the cold storage (40) rises to the cooling upper target temperature and the instant when the cold discharge cooling remaining time becomes zero.
A second aspect of the present invention provides the vehicle air-conditioning system according to the first aspect, wherein when the vehicle engine (4) is in operation, the first calculation means (S100) calculates the stored cold heat, specifically, from information including at least a cold storage time over which the temperature of the cold storage (40) stays below the solidifying point of the cold storage medium (44) so that cold heat is stored into the cold storage medium (44) by means of latent heat of solidification, and the supply rate of the cold air. When the vehicle engine (4) is stopped, the first calculation means (S100) calculates the discharged cold heat from information including at least the elapsed time after the engine is stopped, the suction air temperature of the cold storage (40), and the rate of air passing through the cold storage (40).
A third aspect of the invention provides the vehicle air-conditioning system according to the first or second aspect, wherein the second calculation means (S110) calculates the remaining time, specifically, from a temperature difference between the cooling upper target temperature and the temperature of the cold storage (40) and the amount of change of the temperature of the cold storage (40) per unit time.
A fourth aspect of the invention provides the vehicle air-conditioning system according to any one of the first to third aspects, wherein the remaining time selecting means comprises correction means (S180) for establishing a smooth connection between the remaining time determined by the first calculation means (S100) and the remaining time determined by the second calculation means (S110) when the temperature of the cold storage (40) exceeds the temperature near the solidifying point of the cold storage medium (44).
Consequently, the remaining time determined by the first calculation means (S100) and the remaining time determined by the second calculation means (S110) can be connected smoothly upon switching therebetween. In indicating the remaining time of the cold discharge cooling mode, it is therefore possible to suppress an abrupt change in indication to prevent passengers from feeling odd, that is, from changing from the effect of feeling cool to the effect of feeling warm.
A fifth aspect of the present invention provides the vehicle air-conditioning system according to any one of the first to fourth aspects, comprising indication means (360) for indicating the remaining time selected by the remaining time selecting means (S120, S130, S160, S170, S180). The cold discharge cooling remaining time according to any of the foregoing aspects can thus be indicated to passengers to inform the passengers of the end of the cold discharge cooling mode in advance, i.e., the restarting of the vehicle engine (4).
In addition, the indication can be switched between the remaining times determined by the first and second calculation means (S100, S110), in conjunction with the phase change of the cold storage medium from the solid state to the liquid state. Precise agreement can thus be established between the instant when the cold discharge cooling remaining time equals zero and the instant when a request for the operation of the vehicle engine (4) is issued. Consequently, even when the cold storage medium undergoes phase changes, proper indication of the cold discharge cooling remaining time can be given to passengers so the passengers do not experience any odd feelings related to passenger compartment temperatures or cooling air temperatures.
A sixth aspect of the present invention provides a vehicle air-conditioning system to be mounted on a vehicle which exercises control to stop its vehicle engine (4) when the vehicle stops. The air-conditioning system comprises a compressor (1) to be driven by the vehicle engine (4), an evaporator (9) for cooling air to be blown into the passenger compartment, and being arranged in a refrigeration cycle (R) including the compressor (1), and a cold storage (40) disposed downstream of the evaporator (9) and within the airflow. The cold storage (40) has a cold storage medium (44) to be cooled and solidified by cool air passing through the evaporator (9).
The air-conditioning system enters a cold discharge cooling mode to cool the air blown into the compartment by using cold heat stored in the cold storage (40) when the vehicle engine (4) is stopped, and issues an operation request signal to the vehicle engine (4) when the temperature of the cold storage (40) rises to a predetermined upper target cooling temperature in the cold discharge cooling mode. The air-conditioning system further comprises indication means (360) for indicating, in the cold discharge cooling mode, the remaining time up to which the temperature of the cold storage (40) can be maintained at or below the cooling upper target temperature by using the cold heat stored in the cold storage (40). The cold discharge cooling remaining time can thus be indicated to passengers to inform the passengers of the end of the cold discharge cooling mode, which may correspond to the restart time of the vehicle engine (4).
The parenthesized numerals accompanying the foregoing individual means correspond with the embodiments to be described later. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.